What can file infector viruses do?

Do file infector viruses have the ability to do things like install new programs on your computer or put things like picture or video files onto it? Or is this kind of behavior usually limited to Trojans? Thanks for any help.

File infectors take your existing executables (usually exes but can be other file types even including drivers) and modify them to do something malicious. As for what they can do there is no limit. Infecting files directly is just another way of creating an automatic malware launch point.